Formation of amorphous carbon thin films by plasma source ion implantation

Amorphous carbon films were deposited by methane plasma source ion implantation on silicon wafer and 440C stainless steel substrates. Radio frequency power was used to produce a glow discharge plasma. Ions produced in the plasma are accelerated by high negative voltage pulses (typically -20 kV, 100 Hz, 50 mu s) applied directly to a substrate holder stage. Structure information was obtained on the films by Raman spectroscopy. The composition analysis of the surface layer of the implanted substrates was carried out using Auger electron spectroscopy (AES). The friction coefficients of the films were measured with the aid of a reciprocating sliding tester. The adhesive strength of the films was estimated by a scratch tester. The results showed that the structure of the films varies with the applied voltage. The carbon films produced at high applied voltage exhibited high hardness and very low friction coefficient of about 0.006. The Raman spectra were divided into the "D" disordered peak and "G" graphite peak. The integrated intensity ratio of "D" peak and "G" peak, I-D/I-G, increased at a high voltage. The results of AES revealed that the implanted carbon penetrated the substrate resulting in a complete interfacial mixing. The adhesive strength of the films increased, attributed to the interfacial mixing at the interface. (C) 1998 Elsevier Science S.A.